High levels of free fatty acids (FFA) lead to an increase of liver mitochondrial β-oxidation, which is crucial to drive efficient gluconeogenesis. The mitochondrial oxidation of long-chain FFA requires the intervention of two membrane-bound carnitine-dependent palmitoyltransferases (CPTs). CPT1, the outer mitochondrial membrane enzyme, catalyzes the formation of long-chain acylcarnitines. Liver (L-CPT1) and muscle (M-CPT1) CPT1 isoforms are encoded by two different genes and inhibited by malonyl-CoA. The N-ter domain of L-CPT1 confers its lower sensitivity to malonyl CoA. CPT2, the inner mitochondrial membrane enzyme, reconverts long-chain acylcarnitines into long-chain acyl CoA esters. Long-chain acyl-CoAs are then β-oxidized to acetyl-CoA, which activates the pyruvate carboxylase and gluconeogenesis. According to the mechanism of action described above, pharmaceutically active substances which inhibit L-CPT1 reduce liver β-oxidation, consequently inhibit gluconeogenesis and therefore counteract hyperglycemia.